Outbreak of Fusarium oxysporum f. sp. lycopersici race 3 in commercial fresh-market tomato fields in Rio de Janeiro State, Brazil

Fusarium wilt, caused by three races of Fusarium oxysporum f. sp. lycopersici, is one of the most important tomato diseases. In Brazil, all three races were reported, however, race 3 has been so far restricted only to Espírito Santo State. In the present work, seven F. oxysporum isolates obtained from wilted plants of the race 1 and 2-resistant tomato hybrids 'Giovana', 'Carmen' and 'Alambra' in São José de Ubá and Itaocara (Rio de Janeiro State, Brazil) were characterized at race level. Virulence assays were performed using a set of race differential cultivars: 'Ponderosa' (susceptible to all races), 'IPA-5' (resistant to race 1), 'Floradade' (resistant to races 1 and 2), 'BHRS-2,3' (resistant to all three races). Two wild tomato accessions (Solanum pennellii 'LA 716' e S. chilense 'LA 1967') previously reported as resistant to all Brazilian isolates of F. oxysporum f. sp. lycopersici were also evaluated. Isolates from São José de Ubá and Itaocara were highly virulent to 'Ponderosa', 'IPA-5' and 'Floradade'. They were also able to infect a few plants of 'BHRS-2,3', inducing vascular browning and wilt symptoms. Solanum pennellii and S. chilense accessions displayed an extreme (immune-like) resistant response. These results indicated that all seven isolates could be classified as F. oxysporum f. sp. lycopersici race 3, expanding the geographical distribution of this pathogen within Brazil. The hypothesis of transmission via contaminated seeds is reinforced after the present report, which confirms the almost simultaneous outbreak of race 3 in two geographically isolated tomato-growing areas in Brazil (Espirito Santo and Rio de Janeiro). Evaluation of commercial seed lots imported into Brazil for contamination with the pathogen would be necessary in order to avoid nation-wide spread of this serious disease. A murcha-de-fusário, causada por três raças do fungo Fusarium oxysporum f. sp. lycopersici, é uma das doenças mais importantes do tomateiro. No Brasil, as três raças já foram relatadas, entretanto a raça três encontrava-se restrita apenas ao estado do Espírito Santo. Neste trabalho, sete isolados de F. oxysporum obtidos de plantas com sintomas de murcha, dos híbridos de tomate 'Giovana', 'Carmen' e 'Alambra', em São José de Ubá e Itaocara (estado do Rio de Janeiro) foram caracterizados a nível de raça. Um ensaio de virulência foi conduzido utilizando-se um conjunto de cultivares diferenciadoras de raças: 'Ponderosa' (suscetível a todas as raças), 'IPA-5' (